1. Field of the Invention
This invention relates to marking devices adapted for use with product packaging machines and more particularly to a method and device of applying indicia to product bags which does not hinder or interfere with a product packaging operation.
2. Prior Art
Imprinting devices are in general current use to apply last-minute indicia to pre-printed wrappers or bags, immediately prior to filling the bags with a product, especially perishable food products such as bread or the like. Such last-minute indicia may include dating, pricing or other coded information which cannot be printed at the time the bags are manufactured. Because of the difficulty of applying printing to a stack of bags or after the bags are filled with a fragile product, inflated bag printing devices have been generally utilized to apply last-minute indicia in current packaging operations. Such an inflated bag printing device is described and shown in my U.S. Pat. No. 3,823,664, issued July 16, 1974, entitled "Inflated Bag Printer and Method". Therein, the impriting device is generally utilized adjacent to a bag inflating station where a stack of deflated bags are positioned prior to filling with a product. Each bag, in turn, is inflated by a jet of air directed at an open end of the bag at the top of the stack with the open end maintained in an expanded condition by a mechanical gripping mechanism which also releases the bag from the inflating position and moves it to a bag filling station where an awaiting product is to be packaged. However, prior to moving the bag to the filling station the imprinting device is activated to apply indicia to the inflated bag by taking advantage of the bags' inflating operation which is arranged to move a surface of the bag into contact with a marking face of the imprinter. The marking face is positioned directly above the inflated bag adjacent its closed end whereby activation of an anvil or striker of the imprinter at the closed end of the bag deflates and collapses a portion of the bag to thrust an imprint surface of the bag against the marking face. The anvil is then removed from contact with the bag whereupon the imprinted bag is moved to the filling station by the mechanical gripping mechanism.
While this mode of bag imprinting has been extremely successful in the past, newly developed, high production product packing machines preclude the use of past imprinting arrangements. Herein, a rapid continuous flow of products move along a conveying surface in aligned and spaced relationship to one another, from a receiving station to a discharge station. Intermediate the receiving station and the discharge station inflated bags are placed in the path of the product flow to individually intercept each of the products. Herein, the flow of products along the conveying surface is effective to fill the bags and transport the product filled bag to the discharge station at a relatively high continuous rate. Thus, it will be seen that past imprinting devices which are positioned directly above and behind the inflated bags would interfere with the continuous straight through flow of these highly productive packaging machines.